Improvement in valves for pneumatic signal apparatus



'Wg-u E. PRAM.;

VALVES FOR PNEUMATId SIGNALAPARATUS.

No. 172,492. P 'atenteaan. Y1s, 187e.

V v :Te

www 5.6mm

WITNEssEs; INVENTOR. Uf f ATTORNEY.

UNITED STATES PATENT OFFICEc WILLIAM E. PRALL, OF WASHINGTON, D. o.,AssIGNOR TOAPRALL RAILWAY sIGNAL AND TELEG-EAPH COMPANY, or NEW YORK, N.Y.

.IMPROVEMENT IN VALVES FOR PNEUMATIC SIGNAL APPARATUS.

Specification forming part of Letters Patent No. 172,492, dated January18, 1876; application filed f December 8, 1875.

To all lwhom it may concern:

Be it known that I, WILLIAM E. PRALL, of Washington city, in theDistrict ol' Columbia, have invented a new and useful Improvement inValves for Pneumatic Signal Apparatus, which is fully described in thefollowing specification, reference being had to the accompanyingdrawings.

The object of my invention is to provide a combined diaphragm and valvefor a pneumatic signal system which shall operate to establish directcommunication, first, between the main air-supply pipe of the system andthe piston or other device operating a signal or gate whenever thediaphragm is subjected to pressure; and, second, between the same pistonand an exhaust-vent int-o the outer' air when the diaphragm is relievedfrom pressure.

ln the accompanying drawings, Figure l is a central vertical section ofthe diaphragm and valve, and Fig. 2 a top or plan view of a semi-sectionthereof'.

A is a diaphragm, of rubber, leather, or of thin metal, closely confinedat its edges between two circular plates, B B', which are slightlydished or recessed inwardly to allow' a limited play to the diaphragmbetween them.v C is a cylindrical valve-chest, secured centrally uponthe upper plate B of the diaphragmcasing. This valve-chest is divided bytwo transverse partitions, cl c2, into three chambers, and centralopenings are formed in these partitions, so as to afford freecommunication between all three of said chambers. The lower chamberopens into the space above the diaphragm A, and communicates also withthe outer air by means of an exhaust-vent, f, which may be pierced inthe side of the cylinder, as illustrated in the drawing, or in the upperplate ofthe diaphragm-casing. D is a valvestem, secured centrally to thediaphragm A, and which, extending up into the valve-chest G, carries twocylindrical valves, E and K, which are fitted, respectively, to movefreely,

. yet closely, within the'openings in the twol partitions c1 o2, saidopenings thus being made to serve as bearings for the stem D. The upperedge of the lower valve K, and the lower edge of the upper valve E, areso notched, (see Fig. 1,) and the valves are so proportioned in length,and so secured upon the stem; relatively to each other, as that, whenthe opening in the upper partition c1 is fully closed by its valve E,free communication is established through the opening in the lowerpartition c2, by means of the notches in the lower valve K, asillustrated in Fig. l, the closing of this` valve K operating in likemanner to open the upper valve E. L L are packing-rings, of rubber,leather, or other equivalent material, placed, respectively, at theupper end of the valve E and lower end ofthe valve K, so as to projectradially beyond the same. These rings stop the movement of the valvewhen closed, and overlap the joint between the valve and valveopening,so as to constitute a perfect packing therefor. (See E, Fig. l.) M is asignal airpipe, which extends in one direction to the point from whichit is desired to operate the signal, at which point it is connected withthe air-main by a suitable automatic valve or supply-commutator, whichserves, when prop-` erly actuated, to admit a charge of air to thesignal-pipe, and it extends in the other direction to the point fromwhich it is desired to reverse the signal where it communicates with anexhaust-vent through a second automatic valve or exhaust-commutator,which serves, when actuated, to allow the air in the signalpipe toescape. N is a pipe connecting the upper cham ber of the valve-chestdirectly with the air-main, and O a second pipe connecting the centralchamber directly with the piston or other actuating device of the signalor gate to be operated. P is a plug closing the upper end of thevalve-chest, left open to admit ot' the introduction of the packing-ringL and nut, which secures it above the upper valveopening.

The operation of this improved apparatus is simple and eli'ective: Sosoon as air is admitted to the signal-pipe M, the diaphragm A is thrownup, carrying with it the valve-stem D, whose upward movement will serveto close the communication between the signal-pipe O and theexhaust-vent f, through the central and lower chambers, and to open thecommunication between said signal-pipe O and the main air-pipe N throughthe central and up' per chambers.

The airunder pressure in the pipe N is thus admitted freely to thesignal-pipe 0 to actuate the mechanism with which said pipe isconnected. So soon7 however, as the pressure upon the diaphragm `A isrelieved by an exhaust of the compressed air contained in the pipe M,the valve-rod will instantly drop7 under the intluence of the pressure,upon the lower valve K, and thereby close the Valve E, and, cutting oftcommunication between the air-main N and signal-pipe O, willsimultaneously open communication between said pipe and the exhaust-ventf, and thus allow the compressed air in the pipe to escape.

The rapidity with which the compressed air shall exhaust through theopening f may be so adjusted by means of a suitable cock at the rapidityof the reverse movements of the' mechanism actuated and controlled bythe admission of said compressed air thereto.

I contemplate the substitution of a piston as an equivalent for thediaphragm A.

I claim as my invention- The connected valves E K, combined with a mainpressure-pipe, N5 a signal-pipe7 O, an exhaust-Vent, f, and a diaphragm,A, substantially as and for the purpose herein set forth.

' W. E. PRALL.

' A. H. NoRRIs,

DAVID A. BURR.

